The present disclosure relates to organic photovoltaic monomers, oligomers, and polymers, and more specifically, to methods of synthesizing a number of molecules for use in organic photovoltaics.
Organic electronics have drawn research interest in recent years because of the potential for broad commercial application, including electroluminescence devices, field effect transistors, and organic photovoltaic (“OPV”) devices, among other uses. In all these devices, the key component is organic semiconducting material, which is usually used as one or more active thin layers. OPVs offer a practical path to achieve low-cost, renewable energy. OPVs have several advantages that inorganic counterparts lack that allows for strong potential of lower cost implementation. The advantages of OPVs include the ability to be solution processed into large-area thin-films, to be fabricated into lightweight and flexible devices, and the capacity to tune their properties through organic synthesis.
One problem common to organic solar cells is in achieving polymers and small molecules that are soluble enough in common organic solvents rendering them solution processable, while still maintaining a high degree of crystallinity, which allows for optimal charge separation and transport. This problem is usually dealt with by affixing alkyl side chains to the aromatic molecules that make up the polymer (or small molecule) backbone. The vast majority of polymers that have been successfully used in OPVs include an alternating electron-rich (donor) and electron-deficient (acceptor) comonomers, called donor-acceptor (D-A) copolymers. Typically, it is much easier, for synthetic reasons, to affix alkyl chains to the donor molecules. For this reason, the library of known, alkyl chain-functionalized donor molecules is much more diverse than that of the acceptor molecules. There exists a need for a modifiable acceptor scaffold that can also be easily modified with various alkyl side-chains for improved solubility.